Carburetor



Dec. 25, 1934. A. M. PREN-nss CARBURETOR Filed April 25, 1931 INVENTOR. Ausl/SMV M RefNr/ss BY v v ATTORNEY.

FIG. 2

been employed in carburetors for internal com-1 Patented Dec. 25, 1934 UNITED 'STATES CARBURETOR Augustin M. Prentiss, San Antonio, Tex., assignor to Bendix Stromberg Carburetor Company, South Bend, Ind., (a corporation ofIJllinois 20 Claims.

This invention pertains carburetors and more particularly has reference to acceleration devices therefor.

Acceleration deviceswhich have heretofore bustion engines have been attended with three principal defects, as follows: they have required too great an interval of time for the accelerating fuel charge to reach the mixture outlet of the carburetor which results in a lean spot in rapid acceleration; they have not proportioned the accelerating fuel charge to the speed of opening of the throttle; and they have notregulated the amount of the accelerating fuel charge with the temperature of the carburetor, so that the mixture is voverenriched at high temperatures and underenriched at low temperatures.

An object of this invention is to provide a carburetor 4in which the minimum interval of time is required for the accelerating fuel charge to reach the outlet of the carburetor so that lean spots in rapid accelerating are eliminated.

Another object of this invention is to provide a carburetory in which the accelerating device employs no piston or other moving parts having considerable inertia which delays the vdelivery of accelerating fuel to the outlet ofthe carburetor. t 1 Another object of thi's invention is to provide a carburetor in which a portion ofthe accelerating fuel charge is shunted direct to the mixture outlet of the carburetor so that the time required for acceleration is reduced to a Still another object of my invention is tov provide a carburetor inwhich the acceleration device is adapted to proportion the accelerating fuel charge in accordance with the speed of opening of the throttle so that the slower-the throttle is opened the less will be the accelerating charge.

Still another object of this invention is to provide a carburetor in which the acceleration device is actuated by a vacuum regulated in accordance with the temperature of the carburetor.

A still further object.of this invention is to provide a carburetor in which the acceleration device is operated by a temperature responsive vacuum which is at a maximum at the lowest working temperature of the carburetor and at a minimum atthe highest working temperature thereof.

A still further object of this invention is to provide a. carburetor in which the accelerating device employs a vaeuun acting directly upon the acceleration fuel charge and in which the output carburetor.

With these and other objects in view which may be incidentto my improvements, my invention consists in the combination and arrangef Application April 25, 19,31, 4Serial No. 532,831

ment of elements hereinafter described and illustrated in the-accompanying drawing in which: l, Figure 1 Ishows in centrallongitudinal section a carburetor embodying my improvements;

Figure 2. is a-fragmentary sectional view, on an enlarged scale, ofy the temperature responsive vacuum regulating mechanism; and

Figure 3 is vii. fragmentary sectional view, onv an enlarged scale, of the check valv'e of the acceleration fuel shunt passage.

In Figure 1, the reference numeral 1 indicates the body of a-cnventional Acarburetor comprising the usual'air intake 2, mixing chamber 3, and mixture outlet 4 controlled by a throttle valve 5, which when closed separates said mixing chamber from said mixture outlet. A main nozzle 6- and idle feed 7 communicate through passageways 9 and 10 and port 11 with a lfloat v reservoir 12, which is supplied with liquid 'fuelv through inlet 13 from the main fuel tank (not shown). Float 14 and valve 15 maintain the liquid fuel at aconstant level indicated by the line X-X in the lwell known manner, while a manually adjustable valve 16 seating in port 1l.

controls the main flow of liquid fuel to nozzle 6 and idle ports 7. The reservoir 12 is closed by a cover 17 having an integrallyattached acceleration fuel .chamber 18 which extends partly into reservoir 12 and partly above the cover 17 as clearly. shown in Figure 1. 'Ihe top of chamber 18 abuts against a projection 19 carried by the body 1 adjacent mixture outlet 4, and communicates with the same and with mixing chamber 3 (when throttle 5 is open) by means of a passageway 20 and `port 21.

Rockably mounted within chamber 18 is a iioat 22 which is pivoted at 23 to a lug 24 attached to the wall of chamber 18. Float 22 bears against and actuates a valve 25 which is adapted to 'open and close passage 20 and thus regulate the transmission of suction, from mixture outlet 4 to the acceleration fuel chamber 18. Instead of having doet-22 actuate a valve for'controlling the suction transmitted to chamber 18, this'iioat could' be arranged to actuate a cut-off valve (not shown) controlling the admission of liquid to' chamber P18 after it reaches the desired level.

To the bottom of chamber i 'are attached an normally closed by a spring-pressedball check valve 28 which is adapted to rise and open pipe' 27 whenever the suction in chamber 18 reaches a certain minimum predetermined value.

Upon the opening of valve j28 liquid fuel from reservoir 12 is immediately drawn up into chamber 18 under the prevailing suction which is transmitted from mixture outlet 4 to chamber 18, until the fuel reaches a level indicated at Y--Y in Figure 1 at which level the valve 25 is almost but not quite fully closed. If a higher degree of suction should prevail in the upper part of chamber 18, the liquid fuel therein would begin to rise above the level Y--Y, but this would immediately result in a complete closing of valve and a cutting-0E of the suction in chamber 18 whereupon the liquid fuel therein, being no longer vsustained by said suction, would begin to discharge through outlet pipe 26, thus lowering its level in chamber 18 and again opening valve 25. So long, therefore, as there is a vsuiiicient suction in passageway 20 to lift the liquid fuel from the level X-X in reservoir 12 to the level Y--Y in accelerating fuel chamber 18, liquid fuel will remain in chamber 18 at a level substantially equal to the level Y-Y; On the other hand, as soon as the suction in passageway 20 falls below this value, liquid fuel will commence to discharge through outlet pipe 26, passageway 10 and nozzle 6 and will continue to so discharge until the chamber 18 is empty or until the suction in passageway 20 again assumes a value sufficient to check the discharge or reverse the flow and cause chamber 18 to refill through inlet pipe charge directly into the idlefeed passage 9 whenever the vacuum in chamber 18 permits the liquid fuel level to fall below the level Y-fY Since idle feed passage 9 is provided with an air bleed .30 which permits atmospheric air to enter for the purpose of forming an idle feed emulsion, the degree of vacuum or suction in passage 9-Will nory mally be less than in passageway 20 and chamber 18 (when valve 25 is open) so that when this latter suction is suilicient to hold the liquid fuel at the level Y-Y no flow occurs through cross passage 29. But the instant the suction in passageway 20 begins to fall below that required to maintain the level YY, as when throttle 5 is opened, the liquid fuel in chamber 18 commences to discharge through passages 29 and 26, and so continues until 'the liquid level has fallen below the cross passage 29 and thereafter through passage 26 alone.

The passageway 29 is provided with a ball check valve 31 at its junction -with passageway 9, so that any'fuel discharged from passage 29 will either be `drawn up through idle feed ports 7 or down passage 9 to main nozzle 6, but cannot return to chamber 18. Ball 3l rolls along a V-shaped trough 45 which spans the distance across passage 9 but does not obstruct theflow through said passage. Ball 31 is held on its seat by a helical spring 46, the tension of which is adjusted by a bearing screw 47 so as to cause valve 31 to open at any desired degree of, vacuum in passageway 9. Valve 3l, being normally closed, except when discharging fuel into passageway 9, prevents air entering chamber 18 through passage 29 and in- 4fiuencing the vacuum therein. Reservoir 12 is provided with a vent 32 so that atmospheric pressure obtains -at all times on the liquid fuel in said chamber. 'i

When the engine is running, it is obvious that the degree of vacuum or suction in the mixture outlet 4 is largely dependent upon the position of the throttle 5. It is also to a less extent dependent upon the speed of the engine. If the engine is idling with the throttle in restricted position as shown in Figure 1, there is a relatively high degree of vacuum or suction, in mixture outlet 4` as compared to the vacuum in mixing chamber 3 and the outside atmospheric pressure. If now the throttle be opened slowly, as when the engine is gently or moderately accelerating, there is a gradual lowering of vacuum in outlet 4 and corresponding increase of vacuum in mixing chamber 3 until substantial equilibrium is established between the two at full open throttle. At the same time, the opening of the throttle results in a corresponding increase in speed of the engine (except at full load) and this in turn increases the vacuumor suction in both mixture outlet 4 and mixing chamber 3, so that while the vacuum in mixture outlet 4 tends to fall with the opening of the throttle, if the opening of the throttle is slow so that there is a corresponding increase in speed of the engine, the decrease in vacuum in outlet 4, due to opening the throttle, is almost completely counteract/ed by the increase in. vacuum due to the speeding up of the engine, and the net result of a slow opening of the throttle is a very slight, if any, disturbance of the vacuum in the mixture outlet except under full load, which case will be discussed later.

From what has just been said it follows that a slow opening of the throttle will cause only a slight, if any, lowering of the vacuum in lchamber 18 and hence but avery slight, if any, discharge of accelerating fuel therefrom, but as the speed of opening of the throttle is increased, the drop in vacuum in mixture outlet 4 (and chamber 18) is correspondingly increased, with a consequent corresponding increase in accelerating fuel discharged from chamber 18. Infthis way, the accelerating fuel supply is automatically regulated with the speed of opening of the throttle.

The above description applies to the normal operation of the carburetor where the speed of the engine is approximately responsive to the degree of opening of the throttle. The exceptional condition is where the engine is operating under full load, and the speed is not responsive or proportional to the opening of the throttle, but a wide open throttle is required to keep the engine turning over at slow speed. In this ease the degree of vacuum in mixture outlet 4 decreases as the engine slows down with increasing load, at the same time the throttle must be opened to keep the engine turningV over as the loadincreases, so that the decreasing vacuum in outlet 4 is transmitted to chamber 3 and the two are brought into substantial equilibrium as the throttle approaches .wide open position. But since the speed of the engine does not increase as the throttle is opened, the vacuum in outlet 4 continues to sink until it equals that in chamber 3 which rises somewhat to meet it, as the throttle is opened full. Under these conditions the vacuum in chamber 18 slowly sinks until itis no longer able to maintain the liquid fuel therein at the level Y-Y and as it passes below this value there is a corresponding discharge from chamber 18 (with the opening of the throttle) until chamber 18 isexhausted. Here again the rate of discharge from chamber 18 will depend upon the rat-e of opening of the throttle as the load increases.

' As long as the engine is turning over, however, there is always an appreciable vacuum in chamber 3 and outlet 4 so that there will always be some suction in chamber 18. Hence, if operationfat full load and wide open throttle continues lni ' ference in elevation between the liquid, level in chamber '18 and the top of nozzle 6; the vacuums in chamber 18 and'in nozzle 6 being substantially equal. Since the suction upon the main nozzle at wide open throttle under full load is usually inadequate to create a liquid fuel ilow suiiicient to develop the full power of the engine, it has been customary in the carburetor art to provide a supplementary iiow under these conditions which is automatically cut off as soon asA these conditions cease. This supplementary feed system has generally been known as an economizer and has usually been installed as a separate mechanism from the accelerating` device. Since, however, my accelerating device, as above described, also functions as an economizer under the required conditions, no separate economizer is.necessarylin `my improved carburetor.

Q acceleration decreases in proportion. Hence, I ,provide in my improved carburetor a thermostatic valve to regulate the ow of accelerating fuel in accordance with the temperature of the carburetor. Communicating with passageway 20 is a lateral bore 33 which leads to the outside of the carburetor and is threaded for the reception of l I a screw plug 34 and a valve seat 35, as shown in Figure 2. Plug 34 is provided with a central bore 36 which, with an'aligned bore 37 in valve seat 35, forms a communication from the passageway 20 to the outside atmosphere through a port 37' in a screw cap 38 which is adapted to engage over theend of plug 34.

Slidably mounted in bore 36 and adapted to engage seat 35 is a valve 39, which allows sutilcient clearance in bore 36 to form a free passage: way therethrough. The lower end of valve 39 is tapered to fit into and close passage 3'1 when valve 39 is in its 4 lowermost position. Th upper end of valve 39 is threaded to engage a plurality of adjusting nuts 40 and 41 which embrace the free end of a thermally responsive element 42 fixed to the upper face of plug 34 as with a screw 43. Thermostat 42 is provided with a hole 44 which registers with bore 36 in plug 34 and through which valve 39 passes with sulcient clearance to provide a free passageway from bore 36 to the space enclosed by cap 38. w

Thermostat 42 is so arranged and calibrated as to raise or lower valve 39 a predetermined amount for each degree change in temperature so that the' amount of air drawn through vent 37 into passageway 20, to reduce the vacuum therein, is regulated in accordano ewith the temperature of the carburetor by valve 39.

The action of valve 39 is to proportion the amount'of accelerating fuel charge to the teunl perature of the carburetor, vprogressively diminishing this charge `with increase of temperature, until at a certain predetermined temperature, the accelerating fuel charge is cut oil! altogether.

The operation of my improved carburetor is as follows: when the-engine is started, the throttle is cracked and is substantially in the restricted position -shown in Figure I. The engine is then turned over by the starter. This at once creates a relatively high vacuum in mixture outlet 4, and

. chamber 18, which results in filling said chamber with liquid fuel as described above.

When the vacuum or suction in mixture outlet 4 is high, it is sufficient to hold the liquid fuel in chamber 18 substantially at the level Y-Y. As explained above, this condition of high vacuum in mixture outlet 4 occurs when throttle 5 is restricted (engine idling or running slow) and `also when throttle is substantially fully open and the engine running at high speed. On the other hand, a condition of low vacuum exists in mixture outlet 4 when throttle 5 is suddenly opened (as when rapidly accelerating) and also when the throttle is wide open and the engine is running slow under heavylload. Under conditions of low vacuum in mixture outlet 4 and chamber 18, the suction is too weak to hold theliquid fuel in chamber 18 and it discharges t rough passages 29 and 26. If the vacuum in ch mber 18 decreases rapidly (as when throttle 5 is quickly opened) the into outlet 4 andchamber 3. On the other hand,I

if the vacuum in chamber 18 decreases slowly the liquid fuel in chamber 18 will discharge slowly and if the throttle isopened still more slowly, there is little or no effect upon the vacuum in chamber 18 and no appreciable discharge of L liquid fuel therefrom.

The foregoing operations have been considered upon the basis of valve 39 being fully closed, which is only true when the carburetorg is at its lowest operating temperature and the maximum accelerating charge is desired. Ifnow valve 39 is partly opened, as with increase in temperature, atmospheric air enters 'passage 20, and at once reduces the vacuum in chamber 18 below that in mixture outlet 4, and the further valve 39 opens, the further the vacuum in chamber 18 is reduced, and

vthe smaller the amount of liquid fuel drawn therein. A point is reached (valve 39 full open) where this vacuum is insufficient to draw any liquid fuel from oat chamber l2 up into chamber 18. In

this last case, chamber 18 remains empty regard- CII in chamber 18 is only partially reduced and the output of the accelerating device isl only correspondingly reduced. In this way, the amount of accelerating charge is automatically proportioned to the temperature of the carburetor after the thermostat is once correctly calibrated and set.

While I have shown and described the preferred embodiment of my invention, I desire it to be understood that fI do not limit myself to the constructional details shown by way of illustration, as it is apparent that these may be changed and' modified by those skilled in the art without departing from the spirit of my invention or exceedtrolled suction means for lifting fuel from said reservoir to'said chamber, and gravity means for feeding said fuel from said chamber to said nozzle. 2. In a carburetor having a oat reservoir, an

acceleration fuel chamber, vacuum means for lifting liquid fuel from said reservoir to said chamber, and meanssfor regulating the vacuum admitted to said chamber so as to prevent the liquid fuel therein from rising above a predetermined level.

3. In a carburetor having a mixture outlet, an acceleration device, actuated by the vacuum in said outlet, comprising an acceleration fuel chamber, means for regulating the maximum fuel level in said chamber, and means for regulating suction therein in accordance with the temperature of the carburetor whereby the output from said chamber is inversely proportioned to said temperature. A

4. In a carburetor having a mixture outlet, a acceleration device, actuated by the vacuum in said outlet, comprising an acceleration fuel chamber, means for regulating the maximum fuel level in said chamber, and means for modifying the vacuum therein so that the output of said chami ber is inversely proportioned to the temperature of the carburetor.

`5. In a carburetor, a vacuum operated acceleration device comprising an acceleration fuel chamber and means for gradually reducingthe vacuum therein as the temperature of the carburetor increases so that the output of said device is a maximum at the lowest operating temperature of the carburetor and gradually reduces to a minimum at the highest operating temperature of the carburetor.

6. In a carburetor, a vacuum actuated acceleration device comprising an acceleration fuel chamber, means for regulating the maximum fuel level in said chamber, and thermal responsive means for modifying the vacuum in said chamber so that the output of liquid fuel therefrom is 'inversely proportioned to the temperature of the carburetor.

7. In a carburetor having a mixture outlet ank acceleration device comprising an acceleration fuel chamber subject to theiiuctuations of vacuum in said outlet, means for regulating the maximum fuel level in said chamber, and a thermal responsive air valve for modifying the vacuum` fuel chamber, a passageway leading fromsaid outlet to said chamber whereby the vacuum in said outlet is transmitted to said chamber and a thermostatically controlled air bleed communieating with said passageway for modifying said vacuum in accordance with the temperature of the carburetor, lso that the fuel output of said device is inversely proportioned to the temperature of the carburetor.

y 9. In a carburetor having a mixture outlet, a vacuum operated acceleration device comprising an acceleration fuel chamber, a passageway connecting said outlet and chamber, and a thermal responsiveair bleed for supplying air to said passageway, whereby said device is rendered inoperative at the highest operating temperature of u the carburetor.

10. In a carburetor having a mixture outlet, an acceleration device comprising an acceleration fuel chamber subject to the variations of suction^ in said outlet, a thermostatic needle valve for bleeding air into said mixture outletand modifying the suction in said chamber in accordance with the temperature of the carburetor, whereby the fuel output of said device is inversely proportioned to the temperature of the4 carburetor.

11. In acar-buretor havingv a mixture outlet,

fuel chamber, means for regulating the maximum i fuel level in said chamber, a passageway communicating suction from said outlet to said chamber, a thermostatic4 air valve controlling the admission of atmospheric air into said passageway forV modifying said suction and thereby regulating the output of said acceleration device'.

13. In a carburetor, a combined accelerating device and economizer comprising a supplementary fuel chamber and vacuum means for regulating the discharge therefrom of acceleration and economizer fuel.

14. In a carburetor, a combined accelerating device and economizer comprising a supplementary fuel chamber and vacuum means for regulating discharge therefrom of acceleration and economizer fuel, and temperature-responsive means for controlling the discharge of acceleration and economizer flows in accordance with the temperature of the carburetor.

15. In a carburetor having a main fuel nozzle and an idle fuel feed, an accelerating device comprising an accelerating fuel chamber and combined suction and gravityymeans for discharging accelerating fuel from said chamber through said nozzle and idle feed.

16. In a carburetor having a mixing chamber and a mixture outlet, an accelerating device comprising an accelerating fuel chamber and combined .suction and gravity means for feeding a portion of the accelerating fuel charge from said fuel chamber direct to said mixture outlet and the balance of said chargev to said mixing chamber.

17. In a carburetor having a mixing chamber and a mixtureoutlet, an accelerating fuel chamber and combined suction and gravity means for feeding'a portion of the accelerating fuel charge in said fuel chamber to said mixtureoutlet, without passing through said mixing chamber, whereby the time required for the accelerating charge to reach said outlet is reduced to a minimum.

18. In a carburetor having a main fuel feed nozzle and an idle fuel feed, an accelerating device comprising a float-controlled accelerating fuel chamber and means to discharge liquid fuel from said chamber through said nozzle and idle feed. y

19. In a carburetor having a mixing chamberA and a mixture outlet, an accelerating device comprising an accelerating fuel chamber and oatcontrolledr means for feeding a portion of the accelerating fuel charge from saids fuel chamber direct to said mixture outlet and the balance of said charge to said mixing chamber.

20. In a carburetor having a mixing chamber and a mixture outlet, an accelerating fuel chamber and float-controlled means for feeding a portion of the accelerating fuel charge in said fuel chamber to said mixture outlet, without passing through said mixing chamber, whereby the time required for theA accelerating charge to reach said outlet is reduced to a AUGUSTIN M. PRENTISS. 

